I would agree LAN connection by cable is more reliable than Wireless LAN. It is why we could only connect the server with LAN cable to a switch or an access point. But if you still prefer using a wireless connection, make sure to have a reliable product, run a frequently verify tool  and do more backup of your data files as insurance.

Should your accountant or other users need to access your data file by internet connection, consider deploying a private cloud environment. Your local users may keep accessing the file by LAN and any mobile users may work on the same file at the same time virtually.

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